A heat pump may be reversibly configured to heat or to cool a climate-controlled space. This dual-role capability may allow the heat pump to replace a separate air conditioner/furnace combination. However, because the heat pump uses electricity for both heating and cooling, efficiency (e.g. HSPF) is of utmost importance. Heat pumps sometimes operate in severe weather conditions of freezing precipitation such as freezing rain, snow, sleet, hail, and the like. Most heat pumps use a top discharge fan system located outdoors. The air leaving the heat pump, through the fan, orifice and grill, has been chilled below the ambient temperature. Freezing precipitation can form on outdoor components of the heat pump system, such as, e.g., the fan system and outdoor heat exchanger (HX) coil, which can impair operation of the fan and the heat pump. Further, the ice buildup may cause ice bridging on certain components, which while the components may continue to operate, may operate at a reduced heat and energy consumption efficiency and also create an objectionable noise, prompting one or more occupants to initiate a service call.
Conventional heat pump systems remove frost using a reverse-cycle defrost, in which the heat pump runs in a cooling mode to defrost outdoor (OD) HX coils and components with heat transported from indoor (ID) HX coils. The heat produced by the reverse-cycle defrost is lost to the outdoor ambient thus reducing the efficiency of the heat pump. Moreover, supplemental heat consumed to temper indoor air during the defrost adds further to the energy penalty. Further, the heat pump unit may not require defrosting, but rather simply removing ice buildup or bridging on certain outdoor components.